Telephone-exchange system.



A. E. LUNDELL.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED JAN-l4, 1916.

1,235,705; Patented Au 7,1917.

/n van #0 r1 A/hen E. Lundel/ 'Arry I one office is maintained continuously actu UNITED STATES, PATENT OFFICE.

ALBEN E. LUNDELL, OF NEW YORK, N. Y., ASSIGNOB '10 WESTERN ELECTRIC COMPANY,

4 mconrona'rnn, or new YORK, n.- Y., A conronsrron ornew roam TELEPHONE-EXCHANGE SYSTEM.

change Systems, of which the following is av full, clear, concise, and exact description.

This invention relates to telephone exchange systems, and more particularly to interoflice trunking systems for telephone exchanges. Its object is .to provide for the proper performance of telephonic and vanous. signaling and switch-operating .functions.

According to the main feature of this invention, a disconnect signal associated with ated upon the restoration of a switch employed in the extension of a connect1on 1n the other oflice, means being provided forinterruptedly actuating said signal if a switch, employed in the establishment of the connection in the first office, is restored pr1or -to the restoration of the switch in the other office. By this arrangement an operator,

noticing the flashing of the signal, Wlll know that "she has prematurely taken down the connection and will thus be enabled to reestablish the connection.

The drawing represents the circuit arrangement'of a semi-mechanical system embodying the present invention. The complete equipment and circuits of telephone exchange systems necessary for the establishment of connections selectively between various subscribers lines, not being necessary to a full understanding of the invention,'-are not shown in the drawin There are numerous well-known mec anisms 'for this purpose. It is sufficient to assume that connectlons may be established through several line and trunk switches, the exact number and kind of which may be varied without departure from the invention.

Two subscribers stations 1 and 2 are shown, which may be connected under the control of a connecting operator by way of a spring-jack 3 and a plug switch 4, contacts 5, 6 of an automatic switch, two w res 7, 8

, of a two-wire interoflice trunk, and under the control of another operator through a plug switch 9 and a spring-jack 10., The connecting link between jack 3 and contacts 5,

Specification of Letters Patent.

Patented Aug. 7, 1917'.

. Application filed January 14, 1816. Serial No. 72,149.

6 may bedivided. as usual by a repeating coil 11 into inductive sections, and the trun likewlse by a repeating coil 12.

' The subscriber at substation 1, desiring to lnitiate a call,-removes his receiver from the switchhook, causing thereby the energizatlon of a line relay 13 in the well-known manner, which line rela calling line signal 14. he connecting operator inserts her'pl 4 into jack 3 in which the calling subscri ers .line terminates, establishing thus a circuit from ground through the winding of a relay 1 5, the sleeve contacts of plug 4 and jack 3, andthe winding of a cutoff relay 16 to grounded battery.

Relays] 5 and 16 hecome energized, and the then I operates a latter opens the circuit of relay'13, whereupon lamp 14 isextin 'uished- A further circuit is closed from t e plus pole of battery, through repeating coil winding 17, the tip contacts of plug 4 and jack 3, the calling substation, the ring contacts of jack 3 and plug 4, the winding of a supervisory relay 18, and repeating coil winding19 to the minus pole 'ofbattery. Re1ay'18 closes a shunt around a supervisory'lamp 20.

.The connecting operator sets now contacts 5, 6, of a selector switch of any well-known design, to extend the calling line through a trunk 7, '8 to another operators position. After contacts 5, 6'have been set, the connecting' operator converses with this latter mentioned operator through a well-known call circuit (not, shown). 7 After the second operator has learned the numberof the called subscriber, she inserts her plug 9 into jack 10 in which the called subscribers line terminate s. 11A circuit-is established'thereupon' fromgrounded battery through the winding of the called subscriberscutofi relay 21, the sleeve contacts of jack 10 and plug 9, and the winding of a relay 22 to ground. This relay closes a circuit from the plus pole of battery through its armature and front contact, contact 23 and the power magnet of a sequence switch 24 to the minus pole of batcontact 25 of sequence switch '24, all the sequence switch contacts are closed only in the v Under the control of a normal spring sequence switch positions indicated adjacent to the respective contacts. The sequence switch contact 25 is closed in all the positions of the sequence switch 24, except in the positions indicated adjacent to this contact. Sequence switch contacts 33 and 49 are closed in all the positions of the sequence switch 24.

\Vhen the sequence switch reaches position 4, a circuit is closed from grounded bat- 'tery, through 26, 27, 28, 7, 5, 29, 30 to ground. Relay 27 closes a circuit: the minus pole of battery, 31, contact of relay 27, 32, 33, 34, 35, plus battery. Relay 34 closes a circuit from grounded battery, through 36, 37, 38 and 39 to ground. In position 5 of the sequence switch, the above traced circuit of relay 27 is replaced by a circuit closed through the left-hand contact of re lay 38 and sequence switch contact 40.

In position 10 of the sequence switch, a circuit. is closed from the minus pole of battery, through contact 31, the contact of relay 27, Sequence switch contacts 32 and 41, the windings of relays 42 and 43, and the front contact and armature of relay 22-to the plus pole of battery. Only relay 42 becomes energized, relay 43 being shunted. Relay 42 closes a ringing circuit from ground,'through a ringing current generator 44, the winding of a marginal ringing relay 45, the lower front contact and armature of relay 42, the ring contacts of plug 9 and jack 10, the called subscribers line, the tip contacts of jack 10 and plug 9, and the upper front contact and armature of relay 42 to ground. As soon as the called subscriber removes his receiver from the switchhook, relay 45 becomes energlzed, and

by opening at its back contact the shunt around the winding of relay 43 permits the energization of this relay, which then shortcircuits. relay 42 and causes thus the cutting off of the ringing current and the deenergization of ringing relay 45.

Upon the completed establishment of the connection, a supervisoryrelay 46 becomes energized in the well-known manner and closes a circuit from ground, through its front contact and armature, the right armature and front contact of relay 34, repeating coil winding 47, sequence switch conta'cts 48 and 49, trunk conductor 8, contact 6, the winding of a supervisory relay50, and therepeating coil winding 51 to grounded battery. Relay 5O closes a shunt around a supervisory lamp 52, contact 53 being closed at this time. The closure of contact 53 may be efle'cted automatically under the control of a sequence switch associated with the selector, the wipers of which are indicated at 5 and 6, or manually under the control of the operator. The sequence switch associated with the selector is separate from the sequence switch 24, and operates for controlling the operation of the selector switch in a manner similar to the sequence switch 200 shown in Fig. 1 of a patent to A. E. Lundell, No. 1,168,319, patented J anuary 18, 1916.

When both the calling and called subscribers restore their receivers to the switchhook, relay 18 becomes deenergized and opens the shunt around lamp 20, which will light. Relay 46 also becomes deenergized, opening the circuit of relay 50, which releases and permits supervisory lamp 52 to become lighted. The connecting operator opens now both trunk wires by disconnecting contacts 5, 6, whereupon the circuit of relay 27 is opened, and this relay in turn opens the circuit of relays 34 and 43. Relay 34 connects relay 38 at its contact 54, through sequence switch contact 55 to the trunk wire 8. The path for battery current, however, is open at contact 6, so that relay 38 reacts, opening at its left-hand contact the circuit of relay 27 and closing at its right-hand contact through a sequence switch contact 56 a circuit for sequence switch 24. The sequence switch is moved operator noticing the steady lighting of lamp 59, removes plug 9 from jack 10, cans ing thereby the vdetnergization of-relays 21 and 22.

'Should the operator remove plug 9 from ack 10 prior to the severing of contacts 5 and 6, 2'. 6. while sequence switch 24 is'in position 10; upon the deenergization of relay 22, a circuit is closed from the plus pole of battery, contact of this relay, sequence switch contact 62, lamp 59, and an interrupter 63 to the minus pole of battery. Under the control of this interrupter, lamp 59 is caused to flash, indicating to this operator that she has prematurely removed her plug from the jack, and if she remembers the number of the called subscriber, she is thus enabled to reestablish the connection in due time,

If, for any reason, it is desired to rering the called party, the operator may reestablish the active condition of the ringing mechanism by momentarily depressing a ringing key 64. Prior to this, there had existed a closed signaling circuit through the trunk wire 7, as follows: grounded battery, the left-hand contact of relay 38, 40, 27, 28, ,7, 5, 29, 30, ground"; also a second local circuit: plus battery, 35, 34, 33, 32, the contact of relay 27, 31, minus pole of battery, and a third local circuit: ground, 39, 38, 37, 36, grounded' battery. The depression of the ringing key 64 causes rethrough the armature and back lay 27 to react, opening at its contact the circuit of relay 43 and the secondlocal circuit. .Relay 43 opens the shunt around relay 42 and recloses the shunt about itself. Relay'34 also reacts, opening at its righthand contact the supervisory signaling circuit, closing at .54 a connection for relay 38 to wire 8 of the trunk, and opening at 37 a contact in the third local circuit. Contact 54 makes before contact 37 breaks, so that relay 38 will remain energized, provided it finds a substitute path for bat-- tery current over the trunk wire 8, which it does under the present assumption, the circuit being as follows: ground, 39, 38, 54, 55, 49 8, 6, 50, 51, grounded battery. As

,the ringing key is but momentarily depressed, the original signaling circuit over trunk wire 7 is closed again, and relay 27 acts to reclose the original local ringing circuit, causing the ringing relay 42 to again apply ringing current to the called line. If and when the subscriber again responds, re-. lays 45, 42 and 43 act as before, cutting off the ringing current. The operation of reringing may be repeated as often as required.

What is claimed is:

1. In a telephone exchange system, a plurality of lines, means for extending a calling line toward a called line, a switch for connecting the extended calling line to the called line, a signal associated with said switch, means operative upon .the restoration of said means for continuously actuating said signal, and means operative if said switch is restored prior to the restoration of with said plug, means for continuously actuating said signal if said selector switch is restored and said plug is in use, and means for flashing said signal if said plug is removed while said switch is actuated.

3. In a telephone exchange system, a 'lurality of lines, an automatic selector switch for extending a calling line toward a called line, an operators plug and jack by means of which the extended calling line may be connected to-the called line, a ringing apparatus and a disconnect signal associated with said plug, a two-wire trunk extending between said selector switch and said plug, means operative after the completed establishment of the connection upon the opening of one of the trunk wires for actuating the ringing apparatus a desired number of times, means operative upon the opening of both trunk wires for continuously actuating said disconnect signal, and means operative if said plug is removed prior to the o ening of both trunk wires for flashing said disconnect signal.

' ALBEN LUNDELL. 

